USP Compact NS2 Trigger Not Releasing Hammer

I was just shooting it and on the last shot it ran out of gas and didn't fully cycle the slide which is normal I think? Anyway so then I removed the mag and tried to pull the trigger to release the hammer and the gas release pin thing but it wouldn't release the hammer. It would pull the hammer back a little but that's all. I could still decock the hammer with the decocker though.